Wednesday, August 29, 2012

Do That Thing Like That Sundew Do

Round Leaved Sundew, Drosera rotundifolia
Wetlands present a number of challenges and advantages to their constituent plant communities. Fens and bogs especially have very low nutrient availability due to a combination of water logged soils and high or low pH, but they are areas of high light levels, meaning there is little obstruction to photosynthesis. As such, their associated suites of plants often exhibit a high degree of adaptation to cope and thrive in these conditions. The most striking of these is undoubtedly those plants that have evolved carnivory to deal with the their nutrient-poor environments. Sundew plants are often the most striking of these as, despite their often small size, their fly-paper like leaves turn a wonderful crimson colour as they age. Ireland is home to three species of Sundew, of which the Round Leaved Sundew (Drosera rotundifolia) is the most common (1). The upper surface of the highly specialised leaves, which are arranged in a basal rosette, are covered with tentacles, each of which has a drop of mucus, the sundew, that is composed of complex polysaccharides (2). Insects attracted by the vibrant colours of the leaves an the sundew itself become stuck to the mucus. The tentacles, then wrap themselves around the insect making escape impossible. Proteolytic enzymes secreted by the plant then digest the insect, with any resulting carcass being expelled from the leaf.
Leaf of Round Leaved Sundew, Drosera rotundifolia
D. rotundifolia, along with other Drosera species, has long been used in folk medicine as a treatment for a variety of respiratory problems. Such is the efficacy of the plants that many species are faced with extinction in the wild from over collection (3). Much of D. rotundifolia physiological activity comes from the presence of a number of 1,4-naphthoquinones (4). Many of these have been shown to be inhibitors of seed germination in many plants and to have inhibitory and toxic activity against certain insects and fungi. Investigations into the activity of D. rotundifolia extracts on human cells has shown that it suppresses inflammatory response in mast cells (3). These cells play an important role in allergic and inflammatory reactions. Mast cell-mediated allergic inflammation is involved in many diseases, including asthma by releasing proinflammatory compounds such as cytokines and histamine and any suppression of these responses would be of great benefit to sufferers of that disease.

Round Leaved Sundew, Drosera rotundifolia
  1. Sterry, 2004. Collins Coplete Guide to Irish Wildlife p. 206
  2. Thorén et al., 2003. New Phytologist 159 pp. 507-511
  3. Fukushima et al., 2009. Journal of Ethnopharmacology 125 pp. 90-0696
  4. Hirsikorpi et al., 2002. Plant Science 162 pp 537-542

Monday, August 27, 2012

The Rarest Dragonfly in Ireland

Immature Male Downy Emerald, Cordulia aenea
The rarest of Irish dragonflies is the Downy Emerald (Cordulia aenea), a glorious, metallic green coloured odonate with a clubbed abdomen. While it is common in Britain and other parts of Europe, C. aenea can only be found in a handful of locations in Ireland, all clustered around the Kerry/West Cork region of the country. Even then, it is only encountered near water bodies that are in close proximity to ancient oak woodlands, specifically areas near Killarney and Glengarriff national parks (1).
Immature Male Downy Emerald, Cordulia aenea
I was lucky enough to see and photgraph an immature male at one of these locations recently, something which surprised me quite a deal as they are recorded as emerging in late May, with peak occurrence in mid June. However the wet and windy summer that we have had here may account for this odd timing. The individual pictured was seen on a rare sunny day in Glengarriff Woods Nature Reserve, near Dromdour Lough. Glengarriff Woods is the only location outside of Killarney in Ireland to hold a population of C. aenea (2). Incongruously, however, Dromdour Lough is actually not within the boundry of Glengarriff Park and is in fact within a commercial conifer plantation owned by Coillte, the Irish state sponsored forestry company. Apparently there is a long term aim to recreate the native oak woodland in the area once commercial felling of the mature crop of conifers in complete, something which would very much benefit the population of C. aenea as there is a positive association between this species and woodland, which seemingly provides a feeding habitat for adults (1).
Immature Male Downy Emerald, Cordulia aenea
The individual seen was, as mentioned previously, an immature male and as such lacked the vibrant green colour that is indicative of the species. It was photographed at rest on a wooden railing at the side of a path next to Dromdour Lough and was seen to behave aggressively and chase a male Common Darter (Sympetrum striolatum) which also happened to rest on the railing. This activity continued for at least five minutes, after which the male C. aenea flew off across the lake.

  1. Nelson and Thompson, 2004. A Natural History of Ireland's Dragonflies pp. 226-235
  2. Dúchas, 2002. Glengarriff Woods Nature Reserve information leaflet

Tuesday, August 21, 2012

The Elfin Saddle

Elfin Saddle Mushroom, Helvella lacunosa
Looking more like a dead, decaying leaf than the mushroom that it is, the Elfin Saddle (Helvella lacunosa) is often overlooked for this very reason. It is in fact quite a common species in Ireland, as well as in the west of America and the other countries in Europe where it occurs and can be found under both hardwood and coniferous woods, as well as a variety of disturbed sites (1). The shape of its black coloured cap is quite variable, but often creates a saddle like form, hence its common name. The stem is attractively fluted and can be coloured black through to off white.
Elfin Saddle Mushroom, Helvella lacunosa
While many species of fungi are parasites of vascular plants, H. lacunosa is in fact itself the target species for not just one, but two parasitic fungi, the ascomycete Hypomyces cervinigenus (2) and the gilled fungus Clitocybe sclerotoidea (3). Any defence against these antagonists has as yet not been shown: a novel proteases isolated in from H. lacunosa, helvellasin, has been shown to have no antifungal properties (4).
Elfin Saddle Mushroom, Helvella lacunosa

  1. Kuo and Methven, 2010. 100 Cool Mushrooms  p. 85
  2. Rogerson and Horace, 1971. Mycologia 63 pp. 416-421
  3. Trappe, 1972. Mycologia 64 pp. 1337-1340
  4. Zhang et al., 2010. Journal of Bioscience and Bioengineering 109 pp. 20–24

Thursday, August 16, 2012

A Cheeky Monkey Invader Makes a New Species

Monkeyflower, Mimulus guttatus
Although invasive alien species do threaten native species through competition, one which provides a little compensation in terms of colour is the Monkeyflower, Mimulus guttatus. A pretty, yellow flowered member of the Scrophulariaceae it was introduced to Britain from North America c. 1812, becoming established in the wild by 1824 (1) and making its way across to Ireland soon after. It was first recorded in Co. Cork on the River Bandon prior to 1866 and is now widespread on many of the major waterways within the county (2). As such, it is a paludal species that is quite at home in such wet places that mimic its native north western American home. It has even its home along the river walls of Cork city, with populations visible next to South Gate Bridge and Clarke's Bridge. Growing no more than 20 cm tall (3) it is a perennial, fully seed fertile species, but local colonies are formed by stolon growth. Thus, once established, colonies can grow quite easily. Such ability to colonise has made M. guttatus quite a successful alien and it is now established in New Zealand and 16 European countries (4).
M. guttatus
easily hybridises with other Mimulus species, and while this has been put to use in the development of new garden varieties (some, such as Mimulus × robertsii, have escaped and are now themselves invasives), it is incredible to hear that a hybrid of M. guttatus and a South American relative M. luteus found in the wilds of Scotland has been deemed a new species (4). M. peregrinus, as it has been named by its discoverer Mario Vallejo-Marín of the University of Stirling, Scotland, is fully pollen and seed fertile unlike many other hybrids which are sterile on both accounts. This is seemingly a result of the polyploid nature of M. peregrinus (2n = 6x = 92): previous sterile hybrids have all been triploid . The evolution of this species gives an intriguing glimpse at the possible future for some of our naturalised aliens.

  1. Truscott et al., 2006. Journal of Ecology 94 pp. 1080-1091
  2. Phillips, 1977. Wild Flowers of Britain p. 106
  3. O'Mahony, 2009. Wildflowers of Cork City and County pp. 205-206
  4. Marín, 2012. PhytoKeys 14 pp.  1-14

Sunday, August 12, 2012

Beauty by Name, Beauty by Nature

Male Beautiful Demoiselle, Calyopteryx virgo
The largest Irish damselfly, the Beautiful Demoiselle (Calopterxy virgo), is also (in my opinion) the most beautiful - something to be said when compared with such beguiling creatures such as the Large Red Damselfly and the Emerald Damselfly. A sexually dimorphic species, females are of a lighter hue than males, both a dark metallic  blue-green colour. The wings are a dark brown, but can appear blue or black depending on how the light hits them, and such opaque wings, combined with its slow deliberate flight means C. virgo is commonly mistaken for a butterfly (1).
C. virgo has a distribution through out most of Europe except for the far north (2) and this is also true for Ireland where it is resticted to the south of the country, demarked by a line from Dublin to Clew Bay in Co. Mayo (1). Where it does occur, it often crosses territories with its close relative the Banded Demoiselle (C. splendens). Although similar in appearance, these C. splendens lacks the fully opaque wings of C. virgo (having just a band of colour, hence its common name. C. virgo also has a greener colour, brought about by the wax crystals covering the epicuticle (3).
The close proximity of these relative species often lead to hybridisation (4). Generally, such hybridisation is believe to be driven by sexual selection by females of either species but it has been shown that males, through forced copulation, may be responsible for hybridisation between C. virgo and C. splendens (4).

  1. Nelson and Thompson, 2004. The Natural History of Ireland's Dragonflies pp. 76-83
  2. Gibbons, 1999. Insects of Britain and Europe p. 25
  3. Kuitunen and Gorb, 2011.  Zoology 114 pp. 129-139
  4. Tynkkynen et al., 2008. Animal Behaviour 75 pp. 1431-1439

Saturday, August 11, 2012

Nominated in the Blog Awards Ireland 2012

blog awards ireland
21stcenturynaturalist has been nominated in the "Best Science / Education Blog" section of the Blog Awards Ireland 2012! Thank you to all those who continue to follow and support the blog. Results will be announced at the Blog Awards Ireland 2012 ceremony on the 13th of October, so finger's crossed!

Wednesday, August 8, 2012

Hitching a Ride

Phoretic mites on Mitopus morio
Being a mite, by definition, means you're going to be small. Which is useful in habitats, such as soil, where an ability to squeeze into small soil pores is an obvious advantage. It is therefore not surprising to find that of the 684 species of Acari (mites and ticks) present in Ireland, many of them are microscopic (1). Even those that are comparatively large are rarely over a couple of millimeters in length. Problems arise with this small size when a habitat becomes no longer able to sustain a mite and it needs to move on. Their minute size and soft bodies means that travel over any considerable distance is a daunting and potentially life threatening prospect.

Phoretic mites
So what to do to avoid such perilous journeys? Why, get the bus of course, in a manner of speaking. Certain species of mites, ticks and other arthropods engage in a behaviour known as phoresy, which involves a smaller organism (phoront) hitching a ride form a larger (host) for a limited amount of time (2). Not only does this facilitate movement from areas that are no longer able to sustain the phoront, but it also allows the establishment of new populations in areas that could not otherwise be reached. Often, shelter and/or food are provided indirectly as a result of such a relationship. However contravenes the strict definition of phoresy and can no longer be considered as such. Phoronts are generally smaller (usually much smaller) that their hosts and may occur in large numbers. As a method of dispersal it has existed for quite a long time, with examples existing in Baltic and Dominican amber from 40 million years ago (2).
Mites show the most impressive radiation of phoretic relationships, due mainly to selective pressures brought about by their small sizes. This is further compounded by the transient nature of many of their habitats. As phoronts, they us not only terrestrial hosts, but aquatic and aerial. The picture illustrating this post show two phoretic red mites attached to the rear leg of a harvestman, Mitopus morio.

  1. Ferriss at al., 2009. Irish Biodiversity: a Taxonomic Inventory of Fauna p. 78
  2. Houck, 2009. Encyclopedia of Insects pp. 772-774

Wednesday, August 1, 2012

The African, Asian and European Stonechat

Male Stonechat, Saxicola torquata
Although more common in the west of Ireland than other areas, I recently spotted a group of Stonechats (Saxicola torquata) near Cork city centre, their hard "see tak tak" call identifying them immediately. This call for all the world sounds like two stones being bashed together. I saw both males and females, perched proudly on nearby hawthorn trees and gorse bushes, keeping an eye on me while regularly flicking their tails. Of the two, the male is the most attractive with a black head and a slash of contrasting white across the sides of the throat. Its underbelly is a ruddy orange and has a distinctive white shoulder patch. Females are rustier in colour with duller throat sides.
Female Stonechat, Saxicola torquata
Stonechats have a very large range, extending right across Europe and Asia and down into Africa and as such many subspecies are recognised. The status of these as actual species has lead to mitochondrial DNA (mtDNA) analysis of some 171 individuals from 30 locations across their range. This showed that some subspecies that are very similar in appearance (S. maura maura and S. m. stejnegeri) are not in fact each other's closet relatives. Three distinct subspecies, European (S. torquata rubicola), central Palearctic (S. m. maura) and eastern Palearctic (S. m. stjnegeri) were recognised as likely phylogenetic species. However the fact that in some locations individuals from other groups occurred means that it is unclear if they are indeed biological species.
  1. Sterry, 2004. Collins Complete Guide to Irish Wildlife p. 82
  2. Hayman and Hume, 2002. The New Birdwatcher's Pocket Guide to Britain and Ireland p. 187.
  3. Zink et al., 2009. Molecular Phylogenetics and Evolution 52 pp. 769-773